There are roughly 200,000 partial or complete anterior cruciate ligament (“ACL”) injuries per year in the U.S. The ACL is an intracapsular ligament that cannot spontaneously heal complete tears. Approximately 50% (100,000 U.S. patients) of ACL injuries go untreated either through a lack of diagnosis or repair is deemed unnecessary due to the patient's low level of activity.
Partial ACL tears may heal spontaneously but may heal at an increased length resulting in a positive “Drawer Test” (a commonly used test to detect the rupture of cruciate ligaments in the knee) and the ability of the tibia to shift anteriorly regarding the femur. In the Drawer Test, if the tibia pulls forward or backward more than normal, the test is positive. Excessive displacement of the tibia anteriorly indicates the ACL is likely torn, whereas excessive posterior displacement of the tibia indicates the PCL is likely torn. Complete ACL tears that go unrepaired will cause a positive Drawer Test.
Some surgeons show positive results in healing for some patients with ACL injury through minor surgical intervention by reattaching the ACL.
For the remaining 100,000 patients who undergo ACL repair for complete tears, some studies have shown the strength of the ACL ligament is reduced to approximately 50% of its original strength 6 months after surgery. This may be due to the revascularization of the ACL ligament. At six months, these patients often feel stable enough to return to their previous level of activity. This places the ACL at risk because the patient does not realize the ACL is only at 50% of its original strength.
During normal activity, tension on the ACL may vary. Activities that require sudden stops and changes of direction may place high tension on the ACL or create displacement of the tibia regarding the femur. Adjustment of the tibia relative to the femur, and possibly reduction of ACL tension could benefit the patient in the following ways: (1) reduce additional injury and preserve the length of the partially torn ACL, and (2) reduce the risk of reinjury of the graft for the ACL repaired patient.